1. Technical Field
The present disclosure relates generally to ion implantation, and more particularly, to an ion accelerating device including connection mechanisms with an integrated shielding electrode and related methods.
2. Related Art
Ion implantation is a standard technique for introducing conductivity altering impurities into, or doping, semiconductor wafers. A typical ion implantation process uses an energetic ion beam to introduce impurities (ions) into semiconductor wafers. During ion implantation, a source feed material is energized to generate an ion beam, and the generated ion beam needs to be accelerated by an acceleration column. An acceleration column may be required to accelerate an ion beam at, for example, 670 kV. Preferably, the acceleration is accomplished by the ion beam passing through seven lenses internal to the acceleration column with voltages graded across the lenses due to ion optics requirements.
Active or passive grading schemes are used to control/produce the graded voltages, which require electrical and mechanical connections to the lenses through, e.g., a respective bushing unit. The connection point or termination point, if not protected, is usually a high electrical stress region and can be a weakest point of the accelerating column, which may lead to high voltage failures. As shown in FIG. 6, when a grading circuit board 312 is connected to a bushing unit 314 through a connector 316, at connection point 318, an interface is formed between solid insulation material of bushing unit 314 and/or grading circuit board 312, gas environment 322 that includes air, SF6, or/and other gases, and metal material of connectors 316 (referred to as triple junction). The equal potential line (iso-potential line) 320 is also adjacent to connection point 318 due to the metal material of connector 316. The high electrical stress on connection point 318, defined as (ΔV)/d where ΔV indicates the difference in electrical potentials and d indicates a distance, may cause an electrical discharge. For example, air beaks down at the electrical stress of 75 kV per inch. This electrical stress may exist between the two connectors 316, between connection point 318 and a ground (not shown) and/or between connection points 318 of two adjacent bushing units 314. The electrical discharge may cause electrical failures at connection point 318.